Influenza infection leads to a cytokine storm as the host's immune system fights the virus. This combination of immunity factors has the unfortunate side effect of creating vascular leak. In the case of influenza patients, this vascular leak most often occurs in the lungs and can develop into acute respiratory distress syndrome (ARDS), a condition with high rates of mortality and for which no effective therapy exists. Navigen Pharmaceuticals will develop a novel protein therapy for treating influenza-induced ARDS. This work is based on the discovery by our scientific founder, Dean Li, M.D., Ph.D., that there are endogenous signaling pathways that enhance vascular stability and inhibit multiple cytokines and growth factors from inciting vascular leak and edema. Specifically, Dr. Li has found an endothelial specific receptor, Robo4, that is expressed in mature vessels and is upregulated following endothelial injury from cytokine storm. Robo4 activated by its cognate ligand, recombinant Slit protein, reduces agonist-induced vascular leak in vitro and in vivo. The central goal of this application is to advance the development of a specific Slit protein, Slit2N for the treatment of ARDS induced by influenza viruses. Specific Aim 1: Convert pilot purification methods to processes appropriate for larger scale production of Slit2N. Specific Aim 2: Establish a stable cell line to express soluble Slit2N to provide Slit2N for animal studies Specific Aim 3: Conduct studies in animals infected with H5N1 and H1N1 flu viruses to quantify vascular leak in lungs and determine efficacy of Slit2N in reducing mortality. PUBLIC HEALTH RELEVANCE: Cases of acute respiratory distress in recent influenza pandemics have been particularly high, especially in the case of avian influenza. There is no therapeutic that successfully treats ARDS, and once an influenza patient develops the syndrome, which is often complicated by secondary bacterial infection, mortality is high. Navigen proposes to develop Slit2N, its protein therapeutic that has already shown compelling evidence of efficacy in treating avian flu, for the treatment of influenza-induced ARDS.